/***** s6_12.c*****/
#include<stdio.h>
long fun(int n)
{
	long a;
	if(n>=1)a=n*fun(n-1);
	else{return a;}
}
/*main()
{
int i,n;
long s=0;
printf("please input n: ");
scanf("%d",&n);
for (i=1;i<=n;i++)
s=s+fun(i);
//printf("s=%ld\n",s);
printf("s=%ld\n",fun(n));
}*/

main()
{
	int i,n;
	
	scanf("%d",&n);
	
	printf("s=%ld\n",fun(n));
}